Cable-driven robots (or cable-suspended robots or tendon-driven robots), referred to here as cable robots, are a type of robotic end-effector or manipulator that may be used for various manipulation tasks in a three-dimensional (3D) workspace. Cable robots have included multiple cables attached to a mobile end-effector platform that may carry one or more end-effectors (i.e., manipulators or robots) as illustrated in FIG. 1. The end-effector platform is manipulated by motors that can extend or retract the cables. Generally, cable robots are relatively inexpensive and easy to transport, disassemble and reassemble. Cable robots have been used for a variety of applications, including material handling, haptics, and many others. For examples of material handling applications, see Kawamura et al., Development of an ultrahigh speed robot FALCON using wire drive system, Proceedings of the 1993 IEEE/ICRA International Conference on Robotics and Automation, Nagoya, Japan, Vol. 1, May 1995, pp. 215-220; see also Albus et al., The NIST RoboCrane, Journal of National Institute of Standards and Technology, Vol. 97, Issue 3, May-June 1992; see also Gorman et al., The cable array robot: Theory and experiment, Proceedings of the 2001 IEEE International Conference on Robotics and Automation, 2001, pp. 2804-2810. For examples, of haptics applications, see Bonivento et al., WireMan: A portable wire manipulator for touch-rendering of bas-relief virtual surfaces, Proceedings of the 1997 International Conference on Advanced Robotics (ICAR 97), 1997, pp. 13-18; see also Williams II, Cable-suspended haptic interface, International Journal of Virtual Reality, Vol. 3, Issue 3, 1998, pp. 13-21 (Williams II-1). The contents of the Kawamura, Albus, Gorman, Bonivento, and Williams II-1 documents are fully incorporated herein by reference in their entirety.
Based on the degree to which the cables determine the pose (position and orientation) of the end-effector platform, cable robot systems can be put into two categories: fully-constrained or underconstrained. In the fully-constrained case the pose of the end-effector can be completely determined given the current lengths of the cables. FIG. 2 shows an example of a fully-constrained cable robot, the FALCON-7 (see Kawamura), a small-scale seven-cable high-speed manipulator able to achieve accelerations up to 43 g. Fully-constrained cable robots have been designed for applications that require high precision, high speed/acceleration or high stiffness. Underconstrained cable robots, for example, have been proposed for contour crafting (CC) construction practices (see Williams II et al., Self-Contained Automated Construction Deposition System, Automation in Construction, Vol. 13, 2004, pp. 393-407 (Williams II-2)). The content of the Williams II-2 document is fully incorporated herein by reference in its entirety.
Several other configurations of fully-constrained cable robots also exist (see Williams II-1; see also Maeda et al., On design of a redundant wire-driven parallel robot WARP manipulator, Proceedings of the 1999 IEEE International Conference on Robotics and Automation, Detroit, Mich., May 1999, pp. 895-900; see also Tadokoro et al., A motion base with 6-DOF by parallel cable drive architecture, IEEE/ASME Transactions on Mechatronics, Vol. 7, June 2002, pp. 115-123). However, existing fully-constrained end-effector platforms are not practical for large workspace applications because the overall geometry results in impractical cables, end-effectors, or other components. For example, implementing the FALCON-7 in FIG. 2 on a large scale would require a very large and cumbersome end-effector rod. In addition, fully-constrained cable robots often have cable interference issues, particularly with the cables colliding with nearby objects. The contents of the Maeda and Tadokoro documents are fully incorporated herein by reference in their entirety.
CC is a layered fabrication technology for automated construction of civil structures (see Khoshnevis, Automated Construction by Contour Crafting—Related Robotics and Information Technologies, Journal of Automation in Construction—Special Issue: The best of ISARC 2002, Vol. 13, Issue 1, January 2004, pp. 5-19 (Khoshnevis 1); Khoshnevis et al., Crafting Large Prototypes, IEEE Robotics & Automation Magazine, September 2001, pp. 33-42 (Khoshnevis 2)). The aim of this technology is to improve the speed, safety, quality and cost of building construction. Existing CC methods typically consist of heavy, bulky Cartesian gantry manipulators. The contents of the Khoshnevis 1 and Khoshnevis 2 documents are fully incorporated herein by reference in their entirety.
Similar to other layered fabrication technologies such as rapid prototyping, stereolithography and solid free-form fabrication, CC uses a computer controlled process to fabricate structures by depositing layers of material, building the structure from the ground up, one layer at a time. However, unlike existing layered fabrication processes, CC is designed for construction of very large scale structures, on the scale of single-family homes up to housing complexes and office buildings. FIG. 3 shows a building being constructed using CC as described in Khoshnevis 1.
The CC process involves depositing strips/beads of material (typically a thick concrete/paste type material) using an extrusion process. A nozzle (shown in FIG. 3) extrudes the material in the desired locations. In the original formulation of this system the x-y-z position of the nozzle is controlled by a Cartesian gantry manipulator. As the nozzle moves along the walls of the structure, the construction material is extruded and troweled using a set of actuated, computer controlled trowels. The use of computer-controlled trowels allows smooth and accurate surfaces to be produced. FIG. 4 shows a close-up of the extrusion/troweling tool in a small-scale prototype CC system developed by Khoshnevis (see Khoshnevis 1).
The CC process relies on manipulating the extrusion/troweling nozzle through a very large workspace. Since this manipulation primarily requires only Cartesian motion, a gantry system was used in Khoshnevis 1 to provide motion. However, in Khoshnevis 1, it is recognized that building very large structures requires an extremely large gantry robot, which may be impractical to build. Indeed, such a manipulator would be relatively large and heavy, with massive actuators. It would be impractical to transport and deploy at a construction site.